In a chemical plant, rising pressure in a recovered sodium acetate storage tank caused the tank to rupture and its cover to be thrown nearly 20 m. No other consequence was reported. A safety perimeter of 50 m was established, the content of the tank was transferred into tanker trucks for removal. The accident took place while the plant’s sodium acetate transfer piping was being flushed with nitrogen. The increase in the tank’s pressure was caused by vents that were blocked by a crystalline deposit generated by a secondary reaction. The possible formation of these crystals had not been brought up during the risk analysis of the process. Various measures were adapted to prevent this type of accident from happening again: installation of a weighted cover on the tank, the vent’s diameter increased, modification of the piping purge mode (using water then expanded nitrogen), verification of the unit’s valves, periodic inspection of the vent and cover, and installation of purges on the supernatant organic phase…